"Several law enforcement agencies are working to determine the nature of the threats which caused the aircraft to divert," FBI agent Todd Palmer, of the Salt Lake City division, told CNN.

A man on board the plane that landed in Halifax told the network that passengers were informed that they were being diverted about two and a half hours into the flight "due to operational issues."

He said there was no panic on board and everyone disembarked calmly.

"Upon landing, one of the flight attendants said it was a security issue that needed to get addressed," said the man identified as Yianni.

A passenger on board the Los Angeles-Paris flight said "everything was going swell" for the first two hours until flight attendants began quickly clearing the dinner trays.

- German friendly canceled -

On Tuesday, a bomb threat also forced the cancelation of Germany's friendly against the Netherlands.

Germany's interior minister, Thomas de Maiziere, took the decision to call off the international friendly, based on a "concrete threat," two hours before kick-off in Hanover.

German Chancellor Angela Merkel was rushed back to Berlin, and thousands of fans had to be evacuated from the stadium.

Both the German and Dutch team buses were turned back, as they were five minutes from the stadium when the game was called off.

Despite a thorough search, no explosives were found at the HDI Arena.

It was the second high-profile friendly to be canceled in the wake of Friday's attacks in the French capital, following an earlier decision by Belgian authorities to postpone the country's game against Spain in Brussels amid security fears.

The Islamic State group, which claimed responsibility for the attacks in Paris, has threatened further attacks against France. It also warned in a new video on Monday that countries involved in air strikes against IS targets in Syria would suffer the same fate.

France and Russia have vowed merciless retaliation for the Paris attacks and last month's bombing of a Russian airliner, also claimed by the Islamic State group, which have galvanized international resolve to destroy the jihadists and end Syria's more than four-year civil war.